Recovering green acid soap



A ril 16, 1935.

R. E. BEARD ETAL RECOVERING GREEN ACID SOAP v Filed June 14, 1932 .azbrzcazin ozz Acid Treat 2 Sheets-Sheet 1 Caustic .90da

7Zeatra ljation Finished on .flaflzfied to abcmiaizolo ac. $52504 (92.5%)perl00 greenficidxap Extracted with .DZEUZZQZZ'OR qzc lzt ozz rom Extract filaizqgary Como/28km INVENTORS Robert E. beard Edward. Roberts A'ITORNEY A ril 16, 1935; R, g, BEARD ETAL 1,997,566

- RECOVERING GREEN ACID SOAP Filed June 14, 1932 '2 Sheets-Sheet 2 Effect of/Zcz'digg ofjoap (4007:, V .fieparation 0f Oilfrom wqslwdsoap Distillate Percent afwask irzg Oil Jcparatt'rg from oap ATTORNEY Patented Apr. 16, 1935 UNITED, STATES- PATENT OFFICE .RECOVERING GREEN ACID SOAP Application June 14, 1932, Serial No. 617,128

2 Claims.

This invention relates to the recovery of green acid soaps which have been used for treating emulsions in oil refineries or oil fields, and particularly for treating heavy lubricating oils after sulfuric acid refining. Green acid soaps are/sodium salts of sulfonic acids of low molecular weight, they are preferentially water soluble, and

they-may be prepared as described in 'Humphreys Patent No. 1,474,933, issued November 20, 1923. These green acid soaps are usually produced in the manufacture of highly purified oils, such as white oils and medicinal oils, because the sludge from the treatment of ordinary lubricating oils contains too many undesirable impurities.

Green acid soaps are particularly useful in a number of fields, one of which is the treatment of petroleum oil emulsions. These soaps may be used to break emulsions in accordance with U. S. patentto Rogers No. 1,299,385, issued April 1, 1919, to break sludge emulsions as taught by Diggs, U. S. 1,418,781, issued June 6, 1922, or they may be used for extracting mahogany soaps and other desirable impurities from lubricating oils as taught by Bransky No. 1,396,399, issued November 8, 1921.

After using the aqueous green acid soap solution to treat an acid-treated oil, the soap is unfit for further use. The object of our invention is to recover the green acid soap which has been used for washing acidtreated oils or breaking emulsions, and to render them lit for reuse by removing undesirable components therefrom.

We have discovered that certain light hydrocarbon oils are remarkably effective for extracting. undesirable constituents from green acid soaps when the acidity of the mixture is maintained within predetermined limits. The invention will be more clearly understood from the following description, taken in connection with the accompanying drawings which form a part of this specification and in which Figure 1 is a fiow diagram indicating the general sequence of steps;

Figure 2 is a chart showingthe efiect of acidity of the'soap solution upon the separation of oil from the washed soap solution; and.

Figure 3 shows the efiect of acidity on the extraction of impurities from green acid soap solution. I

In refining lubricating oils the oil is usually treated with concentrated sulfuric acid. The treatment sulfonates a portion of the oil, or certain constituents thereof, and forms (among other things) sulfonic acids of high molecular weight having pronounced emulsifying properties and seriously interfering with subsequent neutralization of the treated oil. Furthermore, the acids are converted into soaps which are preferentially oil soluble and which remain in the oil to contaminate the finished product. A highly effective method for removing these undesirable sulfonic acids and mahogany acids from lubricating oils is to mix the neutral oil with an aqueous solution of green acid soap. This aqueous solution exerts a peculiar solvent efiect on the mahogany soaps, removing them from solution in the oil.

We have found that the resulting solution of green acid soap, mahogany soap and impurities may be acidified and extracted with alight petroleum oil. By properly proportioning the oil and regulating the acidity it is possible to remove the impurities from the green acid soap so that it may be used again for treating additional lubricating oil.

To cite a specific example, a treated motor base stock distillate from Salt Creek crude having a viscosity of 83 sec. Saybolt at 210 F. is neutral ized with caustic soda solution. The mahogany soaps are all extracted by means of about 12 by volume of a 10% aqueous solution of green acid soap. This spent soap, together with the extracted impurities, is then acidified with 92.5% sulfuric acid until the resulting acidity is'about .07-.08 co. in excess per hundred cc. of soap. About 25% by volume of spindle oil is then mixed with the acidified soap solution and the aqueous phaseis separated from the oil phase. The revivified soap in the aqueous phase is then added to additional amounts of the sour, treated motor base stock along with the soda which is used for neutralization. The mixing may be effected by blowing in the usual way with air, after which the mixture is allowed to stand at about F. for several hours. The aqueous green acid soap solution carries down the mahogany soap as before.

Green acid soap separates from the spindle oil in a'very satisfactory manner and the used soap is practically as efiicient as the unused green acid soap in extracting the mahoganycompounds andv other undesirable components from the lubricating oil.

The spindle oil referred to is an acid treated parafiin distillate having a gravity of about 281 A. P. I. Paraflin gas oil having a gravity of 'about 30.5 A. P. I., pitch still distillate having a gravity of about 37.3 A. P. I. or similar light petroleum oils may also be used. Acid treated wash oils are recovered from the soap in greater amounts than untreated oils, oils containing polar groups being especially objectionable.

' White oil" is even better than spindle oil in ob taining clean separation and large recovery yields from acidified, used green acid soap. In a proces of the class hereinabove described it is essential to effect good separation between the green acid soap solution and the light oil phase. We have found that, generally speaking, the amount of wash oil which can be separated from the green acid soap decreases with increasing acidity, as will be noted from the general slope of the curves in Figure 2. These curves, however, show an unexpected peak between an acidity of .05 and .10 cc. excess sulfuric acid (92 /2%) per cc. soap. In other words, at these peaks a maximum oil separation is obtained on the acid side of the curve.

By reference to Figure 3 it will be observed that unless the mixture is acid there will be no appreciable extraction of undesirable constituents. In other words. at an acidity of 0.02 cc. there is four times as much extract in the oil as could be obtained from a neutral or alkaline solution. In view of Figure 3 then, it is evident quantity of light oil and this must be balanced.

from an economic standpoint against the added cost of equipment, manipulation, etc. required for repeated or countercurrent extractions.

The particular apparatus employed forms no part of the present invention and it will therefore not be described in detail. The general steps are indicated in the flow sheet of Figure 1 which is self explanatory. The invention relates more particularly to the idea of means for revivifying spent green acid soap so that it may be reused in the treating of emulsions or the extraction of mahogany soaps from lubricating oils. An important feature of the invention is the regulation of acidity prior to extraction with light oil.

While we have described the invention in detail it should be understood that we do-not limit ourselves to the specific conditions hereinabove set forth except as defined by the following claims which should be construed as broadly as the prior art will permit.

We claim:

1. In the method of extracting mahogany com pounds from green acid compounds with light oils, the step which comprises adjusting the acidity of the mixture to about the equivalent of .05 to .10 cc. of 92.5% sulfuric acid per hundred cc. of soap solution and extracting the mixture at this critical acidity with a light oil.

2. The method of revivifying spent green acid soap which has been exhausted as a treating reagent for lubricating oils because of contamination with mahogany soap and other impurities, 

